scope:

This document defines general principles for assessing an extension of service life beyond the original service life of subsea systems.

This can require an extension of the design life premised in the original design.

Sub-systems and components included within a subsea system are:

- subsea XT (Annex D);

- subsea structures (Annex E);

- subsea valves (Annex F);

- subsea manifold piping systems and interconnecting pipeline (Annex G);

- subsea umbilicals and power cables(Annex H);

- subsea control systems (Annex I);

- tether and buoyancy (Annex J).

The scope distribution is graphically illustrated in Figure 1.

EXAMPLE Service life and design life are defined with some difference in identified standards. Some examples are quoted here:

DNV-ST-F101 [3]: Design life is the initially planned time period from initial installation or use until permanent decommissioning of the equipment or system. The original design life can be extended after a re-qualification.

ASME B31.8 [4]: Does not define a design life, but uses design life and service life as dimensional limits for design with respect to cyclic loading and cathodic protection systems.

ASME B31.4 [5]: Design life is a period of time used in design calculations selected for the purpose of verifying that a replaceable or permanent component is suitable for the anticipated period of service. Design life does not pertain to the life of the pipeline system because a properly maintained and protected pipeline system can provide liquid transportation indefinitely.